Numerous servo valve configurations are known in the prior art. U.S. Pat. No. 6,199,588 entitled “Servovalve Having a Trapezoidal Drive” discloses a servo valve having a trapezoidal shaped drive element for interfacing an electric motor to a valve spool attached to a bias spring.
U.S. Pat. No. 6,000,678 entitled “Motor/Spool Interface for Direct Drive Servovalve” is directed to a direct drive servo valve having a motor shaft with an engagement member which causes a valve member to reciprocate with rotation of the shaft.
U.S. Pat. No. 4,742,322 entitled “Direct Drive Servovalve with Rotary Force Motor” teaches a direct drive servo valve having a limited angle rotary force motor. The motor has an output shaft with an eccentric arm with a ball for interfacing with a valve spool.
U.S. Pat. No. 4,641,812 entitled “Direct Drive Valve and Force Motor Assembly Including Interchangeable Stator Assembly and Alignment System or Method” discloses a direct drive servo valve having a magnetic spring and a flexible drive shaft with an eccentric to convert rotation motion to linear motion. The valve assembly includes a calibration nut for adjusting the hydraulic valve null relative to the magnetic spring null.
U.S. Pat. No. 4,951,549 entitled “Differential Cylinder Pressure Gain Compensation for Single Stage Servovalve” discloses a digital servo valve having an electric DC stepping motor connected to a ball screw mechanism for converting motor rotation into displacement of a hydraulic four-way spool valve. The assembly includes a torsion bar fixed to a valve spool coupling journal.
U.S. Pat. No. 5,031,653 entitled “Differential Cylinder Pressure Gain Compensation for Single Stage Servovalve” discloses a single stage reciprocating valve spool attached to mechanical feedback springs. The valve spool is driven by an electrically controlled torque motor.
U.S. Pat. No. 5,263,680 entitled “Motor-To-Spool Coupling for Rotary-To-Linear Direct Drive Valve” discloses a valve having a coupling between an electric motor and a valve spool for converting rotary to linear motion. The motor contains a shaft with a pin intimately coupled to a shaped, outwardly expandable bushing having flat and arcuate surfaces.